The proposed investigations are designed to gain new basic knowledge about the regulation of the blood coagulation, fibrinolysis, and kinin-generation pathways. For these studies, human plasma proteins will be isolated and characterized in terms of their chemical, physical, immunochemical and biological properties. This proposal is an extension of our work that led to new ideas about the surface-dependent activation of Hageman factor and its pathways involving high MW kininogen, prekallikrein and FactorXI. Details of molecular interactions between these proteins will be studied and the intrinsic enzymatic activity of the single chain forms of Hageman factor and prekallikrein will be assessed. To assess critically current concepts of the intrinsic and extrinsic coagulation pathways, purified radiolabelled proteins (Factors XII, XI, IX, and X, prekallikrein, and high MW kininogen) will be added to normal and deficient plasmas and studied when clotting is initiated by either kaolin or thromboplastin. Preliminary data from studies of the thromboplastin-dependent cleavage of 3H-Factor X in clotting plasma support the new hypothesis that the physiological extrinsic coagulation pathway involves Factors IX and VIII. Studies of the thromboplastin-dependent cleavage of 3H-Factors X and IX in normal and deficient plasmas will test this new hypothesis and provide new knowledge about the extrinsic pathway. New approaches will be taken to identify and isolate plasma proteins that participate in Hageman factor-dependent and Hageman factor-independent fibrinolytic pathways. Dextran sulfate-dependent fibrinolysis will be studied in the presence of synthetic fibrinolytic agents (derivatives of flufenamic acid) that inactivate plasma protease inhibitors. The use of such synthetic fibrinolytic agents, in combination with efforts to fractionate plasma proteins, may unmask activities and pathways that were previously obscured by potent protease inhibitors. These studies should provide new information about intrinsic fibrinolytic pathways.